Study On The Equilibrium Of Solid And Solid Mixture In Supercritical CO₂

During the past thirty years, great progress has been made in the theory and application of supercritical fluid science and technology. Now the study on the equilibrium of solid and solid mixture in supercritical fluid continue to be a very important part in the fields of the supercritical fluids because it can provide key informations for designing and building up any practical supercritical separation processes. Therefore study on the equilibrium of solid and solid mixture in supercritical CO₂ with and without cosolvent has been carried out to deepen the fundamental research, and the major works is presented as follows:Based on the study on the equilibrium of single solute in supercritical fluid, a new analytical method , the high performance liquid chromatograph (HPLC) method was developed to determinate the components of the mixture in supercritical multi-system, which has made a solid foundation for the coming-up study on the equilibrium of solid mixture in supercritical multi-system.As for the experimental research aspect, the influence of operational condition on the solubility of single solute or solid mixture in supercritical fluid has been fully investigated in this thesis. The investigated single solute included p-methylbenzenesulfonic acid, ethyl p-hydroxybenzoate and ethyl p-aminobenzoate, and the investigated solid mixture system is ethyl p-hydroxybenzoate + ethyl p-aminobenzoate (1:1 equal-molar mixed). The cosolvent effect of pure methanol, ethanol, normal propanol, normal butyl alcohol, acetone, and ethyl acetate to the pure solute or solute mixture is included here. The mixed cosolvents effect of ethanol + ethyl acetate (1: 1 equal-molar mixed) is also discussed. The experimental temperatures are 308, 318 and 328 K, and the pressure ranging from 8 to 21 MPa.The effect of temperature, pressure, molecular structure on the solubility of single solute in pure supercritical CO₂ was investigated, and the influence of temperature, concentration on the effect of single or mixed cosolvent was also studied.For the study of solid mixture in the ternary system, each component in the mixture can be treated as a special "solid cosolvent" for the other one, and the result show that the solubility of a given solid in a ternary system increased relative to the value of the corresponding binary system, and was in proportion to the solubilities of the other solid in the ternary system. The reason for the solubility enhancement of each component is explained The selectivity of supercritical CO₂ to the solid mixture is discussed. The cosolvent effect of alcohol series cosolvent to the ternary system was investigated with the propose to enhance the selectivity in the ternary system.